Why lexiav is always deletes one 1 dwarf?

Why lexiav is deleting always one 1 dwarf?

As you might notice lexiav's deleting 1 dwarf always when he reach Bastion castle as video shown below.

I'm not sure why is he doing that but I think it's kind of a ritual some like some football player has.

This action no make sense at all and it's not any ester egg or anything.